Wax—Wax rings are the most common, but they can only be used once. If you change the position of the toilet after setting it down, the ring will become deformed.
Plastic—Plastic rings allow the toilet to be removed and adjusted without having to replace the ring. Plastic rings for toilets fit flanges up to 3/4" below the finished floor. Adhere them to the toilet before positioning the toilet and setting it down.
Rubber—Rubber rings allow the toilet to be removed and adjusted without having to replace the ring. Rubber rings for floor-mount toilets do not require adhesive. They fit flanges that are up to 1/2" below the finished floor.